indexed allocation method is the best access method. With diagram and disadvantages and advantage of indexed allocation method

1. INTRODUCTION
 It brings all the pointers together into one
location called Index location.
 Each file has its own index block, which is an
array of disk-block addresses, the ith entry in the
index block points to the ith block of the file.
 Each file has its own index block, which is an
array of disk block addresses the ith entry in the
index block points to the ith block of the file.

2.  To read the ith we use the pointer in the ith
index entry to find and read the desired block.
 When the file is created all the pointers in the
index block are set to nil
 When the ith block is first written, a block is
obtained from the free space manager, and its
address is put in the ith index entry

4. ADVANTAGE
 No external-fragmentation problem.
 Solves the size-declaration problems.
 Supports direct access

5. DISADVANTAGE
 Used only for sequential access of files.
 Direct access is not supported
 Memory space required for the pointers.
 Reliability is compromised if the pointers are lost
or damaged